Disazo dyestuffs and process of making same.



' inarkable fastness.

EBHST ZEHIITNER, 0F BASED, SWITZERLAND, ASSIGNQR T0 DYE WORKS, FOE-MERLY L. DURAND, HUGUENIN a 00.,

OF BASEL, SWiTZEBLAND. I

DISAZD DYESTUFFS AND PROCESS 0F MAKING Lll'lf fr s l.

21o Drawing.

To all whom it may concern Be it known that I, ERNST ZEHNTNER, doctor of philosophy and chemist, a citizen of'the Swiss Republlc, and resident of Basel, Switzerland, have invented New Disazo Dyestuffs and a Process of Making Same, of which the following is a full, clear, andexact specification.

United States Letters Patent 329638 and 39484-1 disclose the manufacture of disazo dyestuffs by coupling tet-razodiphenyl with salicylic or ortho -cresotinic acid. These dyestufi s are very sparingly soluble and are only gradually absorbed by cotton. On account of their sparing solubility they have found no application for cotton printing, as they yield only unimportant tints which have but little resistance to soap.

According to the present invention by coupling tetrazotized benzidin-2,:2-disulfonic acid with an oxycarboxylic acid of the benzene series, such as salicylic acid or orthocresotinic acid, yellow disazo dyestuffs are obtained which correspond to the formula: I

scan (in which Ptstands {or the radical of an ortho-oxy-carboxylic acid of the benzene series) and are inform of their alkali salts suitable for the purposes of dyeing well as, in particular, for cotton printing on account of their easy solubility and their re- This result was unexpected, as the dyestufi'sfrom and salicylic acid or orthocresotinic acid, in spite test of their sparing solubility, are but litt to to soap when used in cotton printing;

OaTvI Specification of Letters Patent.

out, filtered and dried.

Patented Got. it, 11913.

Application filed December 10, 1912. Serial No. 735,963.

' deed'it was anticipated that by introducing two sulfonic groups, the dyestuffs would be still less fast to soap. The new dyestuffs are, however, remarkably fast to soap, soda, chlorin, light and surpass in these properties all hitherto known azo dy'estuils used in cotton printing.

A particularly valuable property of the new dyestuffs is that when they have been printed and steamed, washing with water removes absolutely no dyestufl that is to say the washing water remains colorless.

The following example illustrates the invent1on: 34.4 kilos of benzrdin-QzW-disulfonic acld NH2 um I sc n $02K are dissolved in 300 liters of water with aid of 8 kilos of caustic soda or 10.6 kilos of calcined sodium carbonate and after addition of a concentrated solution of 14 kilos of sodium nitrite the whole is poured into a mixture of 50 kilos ofiihydrochloric acid of 22 Be. and 100 kilos of ice, while stirring well, and maintaining the temperature at about 35 by adding ice. The

greater part of the tetrazodi'phenyldisuh I tonic acid separates. When the pouring is at an end the stirring is continued for some time and. then the thin paste is introduced into a cold sol'utionof 28 kilos of-salicylio acid in 30 kilos of calcined sodium carbonate and 150 liters of water. The coupling is finished inknown manner by addition of caustic soda lye and the dyestufi" is salted The dyestufi' which corresponds to the formula scan What I claim is:

l. The herein described process for the.

manufacture of disazo dyestufis consisting in combining the tetrazo derivative of bond din-2:2'-disu'lfonic acid with orthoroxy 

